1. Field of the Invention
This invention relates to a coil bobbin and to a transformer employing the particular coil bobbin, and, more particularly, to a coil bobbin minimized in size and capable of stably and safely holding lead wires of a coil wound on the bobbin, as well as a small transformer employing this small coil bobbin with a holding arrangement for lead wires of the coil strengthened.
2. Description of Related Art
In manufacturing the transformer, conventionally, as shown in FIG. 5A, a pair of lead wires 111 of a coil on the coil bobbin 100 are hung to a pair of notches 101 provided at an inside corner edge of a terminal base which is on a flange and having terminal pins 102, and then the lead wires 111 are respectively wound on each of the terminal pins 102. Since, in this case, the lead wires 111 are only passed through the notches 101, the wires are apt to move out of the notches to shift on the surface of the bobbin 100, which causes breakage of the wires.
In order to prevent the lead wires from shifting and breaking, a Japanese Laid-Open Patent Publication No. 2002-353040 has suggested a coil bobbin 200 as shown in FIG. 5B, in which a coil bobbin 200 is provided with a terminal base with a pair of grooves 201 extending along in the thickness direction of the flange, i.e., in an axial direction of the bobbin to lie between inner and outer side faces of the terminal base and deep in radial direction of the flange, and with a pair of bosses 221 on the outer side of the terminal base. The load wires 211 are passed respectively through each of the grooves 201, hung around each of the bosses 221 and then led to each of the terminal pins 202 to be wound thereabout. With the use of such long grooves 201 and bosses 221 as above, the lead wires can be stably held, which prevents shifting and breaking of the wires.
The known coil bobbin as described above still has such problem that, as the transformers are minimized in dimensions, the coil bobbin has to be also minimized to have a smaller space for providing the bosses and eventually the bosses have to become smaller. Such minimization of the bosses causes lowering the strength of the bosses and the bosses become more subject to breakage with the lead wires hung on them, and then the lead wires will be subject to shifting and damaging.
The present invention has been suggested to solve the foregoing problem, and an object of the present invention is to provide a coil bobbin capable of stably holding the lead wires in position to positively prevent them from being caused to shift or to be loosened to be damaged, and also to provide a transformer employing such coil bobbin.